The present invention relates generally to magnetic tape transport systems and more particularly to apparatus for remotely or locally controlling the motor tape drive mechanism of an audio tape recorder or the like. The apparatus of the present invention is also effective to provide proper tape tensioning and differential braking of the opposing forward drive and rewind motors and also includes means for bringing the tape drive to a stop without snarling the tape in case of a power failure.
Reference may be made to the following U.S. Pat. Nos.: 3,769,470; 3,673,473; 3,478,985; 3,435,310; 3,435,314; 3,347,996; 3,785,588; 3,779,384; 3,764,087; 3,746,278; 3,734,426; 3,733,529; 3,729,146; 3,715,641; 3,704,401; 3,491,968; 3,488,696; 3,487,374; 3,482,229; 3,424,392; 3,409,240; 3,400,895; 3,329,876; 3,244,954; and 3,206,133.
The applications in which it may be necessary or, at the very least, desirable to provide for the remote control of the tape drive mechanism in tape recorders and the like are many, but one particular area of concern is in the field of telephone answering machines. There, the user is often away from home or his place of business, leaving it unattended, and must call in to receive messages recorded in his absence which may, in turn, dictate his subsequent course of action. If the user cannot exercise remote control over the answering machine to playback the recorded messages over the telephone, he will have to return to his home or office to receive the message. This, of course, may result in missed appointments and other inefficiencies.
Previous remote control tape transport mechanisms for remote control applications, however, have used complex relay arrangements to control switching paths to the a.c. drive motors and have also included bulky storage capacitors as energy storage devices to be used for braking the reels when the tape is stopped. Such systems, however, consume large amounts of power and require that an a.c. voltage source be provided. Similarly, the tape drives utilized in many computer systems also rely on an elaborate system of servo-mechanisms to provide proper drive to the tape.
With the advent of tape cassettes, smaller drive mechanisms have been provided. However, present remote control systems for cassette mechanisms use an elaborate system of solenoids which in themselves consume large amounts of power and are subject to limited mechanical life. This is particularly disadvantageous in central office telephone answering applications where often only a d.c. potential voltage source is available and where low power consumption is mandatory.
In addition to the common functions to be provided, such as switching the tape drive mechanism between the "rewind," "fast forward," "play," and "record" modes, any remotely controlled, or for that matter any locally controlled, tape drive mechanism should also include means for properly tensioning the tape as it is transported past the record and/or playback head(s) to insure accurate sound reproduction and to prevent tape snarling. Means should be included for braking the forward drive motor and rewind motor, which are respectively used to drive the tape take-up reel and the rewind reel, without spilling the tape when the machine is switched to the "stop" mode from the "rewind" or "fast forward" modes or in case of a power failure.